Water heater constant temperature control method and device based on variable water temperature and water heater

Abstract

The application discloses a water heater constant temperature control method and device based on variable water temperature and a water heater, and the method comprises the following steps: acquiring the operation parameters of the water heater; determining the real-time power theoretical value and the power control fuzzy value of the sampling time according to the operation parameters; determining a first incremental PID control model according to the operation parameters and a water temperature control mathematical model; processing the temperature difference between the set temperature and the outlet water temperature based on the first incremental PID control model to obtain a first compensation power control output value; correcting the first compensation power control output value according to the power control fuzzy value to obtain a first compensation power correction output value; determining a target power value according to the first compensation power correction output value and the real-time power theoretical value; and driving the heating module to perform heating according to the target power value. The water temperature control mathematical model is established, the incremental PID control model is derived, the fuzzy control is combined, the stability and robustness of the outlet water temperature are improved, and the response time is shortened.

Description

Technical Field

[0001] This invention relates to the field of water heater heating control technology, and in particular to a water heater constant temperature control method, device and water heater based on variable water temperature. Background Technology

[0002] An instant water heater is a device that rapidly heats running water using electronic heating elements. Instant water heaters have the advantages of maintaining a constant water temperature and heating water quickly, and are widely used in daily washing, bathing, and other scenarios.

[0003] The key to the water output performance of instant water heaters lies in constant temperature calculation. When there is a temperature difference between the output water temperature and the set temperature, a constant temperature algorithm is used to correct the temperature difference and ensure that the correction effect can be sustained.

[0004] Existing water heater temperature control algorithms typically employ either logic calculations or PID control algorithms. The pure logic calculation method, which controls temperature based on each calculation deviation, suffers from slow response times and inaccurate calculations. It only activates temperature control when a deviation exists, resulting in poor temperature control performance. The existing PID control algorithm, which adjusts its parameters based on temperature differences, also exhibits slow parameter correction and a slow response to temperature changes, leading to significant overshoot and impacting temperature control effectiveness. Summary of the Invention

[0005] This invention provides a constant temperature control method for water heaters based on variable water temperature, which solves the problems of slow response speed and poor constant temperature effect of existing constant temperature control algorithms, and helps to improve the adjustment response speed and improve the constant temperature effect.

[0006] In a first aspect, embodiments of the present invention provide a method for constant temperature control of a water heater based on variable water temperature, comprising the following steps:

[0007] Obtain the operating parameters of the water heater, including the set temperature, inlet water temperature, outlet water temperature, water flow parameters, and voltage parameters;

[0008] The theoretical real-time power value and power control fuzzy value at the sampling time are determined based on the operating parameters.

[0009] A mathematical model for water temperature control was established based on the principle of energy conservation.

[0010] The first incremental PID control model is determined based on the operating parameters and the water temperature control mathematical model.

[0011] Based on the first incremental PID control model, the temperature difference caused by the water temperature change is processed to obtain the first compensated power control output value;

[0012] The first compensated power control output value is corrected based on the power control fuzzy value to obtain the first compensated power correction output value;

[0013] The target power value is determined based on the first compensated power correction output value and the real-time theoretical power value;

[0014] The heating module is driven to perform heating according to the target power value.

[0015] Optionally, determining the real-time theoretical power value and power control fuzzy value at the sampling time based on the operating parameters includes the following steps: establishing a preset fuzzy value table based on the water flow rate and temperature difference; obtaining the temperature difference between the set temperature and the outlet water temperature and the inlet water flow rate; and determining the power control fuzzy value by looking up the preset fuzzy value table based on the inlet water flow rate and the temperature difference.

[0016] Optionally, determining the real-time theoretical power value and power control fuzzy value at the sampling time based on the operating parameters includes the following steps: determining the real-time power coefficient based on the voltage parameters; and determining the real-time theoretical power value based on the real-time power coefficient, the set temperature, the inlet water temperature, and the water flow parameters.

[0017] Optionally, the water heater constant temperature control method based on variable water temperature further includes the following steps: determining a positional PID control model with hysteresis compensation based on the operating parameters and the water temperature control mathematical model; processing the temperature difference between the set temperature and the outlet water temperature based on the positional PID control model with hysteresis compensation to obtain a power control output value; and determining a target power value based on the first compensated power correction output value, the power control output value, and the real-time theoretical power value.

[0018] Optionally, determining the positional PID control model with hysteresis compensation based on the operating parameters and the water temperature control mathematical model includes the following steps: adjusting the parameters of the water temperature control mathematical model according to the water flow parameters to obtain a real-time water temperature control mathematical model; determining a hysteresis compensation model based on the real-time water temperature control mathematical model; adjusting the positional PID control parameters based on the water flow parameters, and determining the positional PID control model based on the parameter adjustment results; and establishing a positional PID control model with hysteresis compensation based on the hysteresis compensation model and the positional PID control model.

[0019] Optionally, processing the temperature difference between the set temperature and the outlet water temperature based on the positional PID control model with hysteresis compensation to obtain a power control output value includes the following steps: obtaining a predicted deviation function between the set temperature and the outlet water temperature based on the hysteresis compensation model; obtaining the actual temperature difference between the set temperature and the outlet water temperature; determining a predicted temperature difference based on the actual temperature difference and the predicted deviation function; and determining the power control output value based on the predicted temperature difference using the positional PID control model.

[0020] Optionally, the water heater constant temperature control method based on variable water temperature further includes the following steps: determining a second incremental PID control model based on the change in the water flow parameters; processing the temperature difference between the set temperature and the outlet water temperature based on the second incremental PID control model to obtain a second compensated power control output value; performing a weighted summation of the first compensated power correction output value, the power control output value, and the second compensated power control output value based on a preset neural network model to obtain a combined power output value; and determining a target power value based on the combined power output value and the real-time theoretical power value.

[0021] Optionally, the water heater constant temperature control method based on variable water temperature further includes the following steps: obtaining a preset single-step limit value; determining whether the target power value exceeds the preset single-step limit value; if the target power value exceeds the preset single-step limit value, then using the preset single-step limit value to replace the target power value and driving the heating module to perform heating.

[0022] Secondly, embodiments of the present invention also provide a water heater constant temperature control device based on variable water temperature, comprising: a detection unit for acquiring operating parameters of the water heater, the operating parameters including set temperature, inlet water temperature, outlet water temperature, water flow parameters, and voltage parameters; a theoretical calculation unit for determining a real-time theoretical power value and a power control fuzzy value at the sampling time based on the operating parameters; a model acquisition unit for establishing a water temperature control mathematical model based on the principle of energy conservation, determining a first incremental PID control model based on the operating parameters and the water temperature control mathematical model; processing the temperature difference caused by water temperature changes based on the first incremental PID control model to obtain a first compensated power control output value, and correcting the first compensated power control output value based on the power control fuzzy value to obtain a first compensated power correction output value; a power correction unit for determining a target power value based on the first compensated power correction output value and the real-time theoretical power value; and a heating drive unit for driving the heating module to perform heating according to the target power value.

[0023] Thirdly, embodiments of the present invention also provide a water heater, including the above-mentioned water heater constant temperature control device based on variable water temperature.

[0024] The water heater provided in this invention includes a variable-temperature water heater constant-temperature control device. This device executes a variable-temperature water heater constant-temperature control method. It acquires the water heater's operating parameters and determines the real-time theoretical power value and power control fuzzy value at the sampling time based on these parameters. A water temperature control mathematical model is established based on the principle of energy conservation. A first incremental PID control model is determined based on the operating parameters and the water temperature control mathematical model. The temperature difference caused by water temperature changes is processed based on the first incremental PID control model to obtain a first compensated power control output value. The first compensated power control output value is corrected based on the power control fuzzy value to obtain a first compensated power correction output value. A target power value is determined based on the first compensated power correction output value and the real-time theoretical power value. The heating module is then driven to perform heating based on the target power value. This solves the problems of slow response speed and poor constant-temperature effect of existing constant-temperature control algorithms. By combining incremental PID control and fuzzy control, the response speed of power adjustment is improved, the stability and robustness of the outlet water temperature are enhanced, and the constant-temperature effect is improved. Attached Figure Description

[0025] Figure 1 This is a flowchart of a water heater constant temperature control method based on variable water temperature provided in Embodiment 1 of the present invention;

[0026] Figure 2 This is a schematic diagram of the control principle of a water heater constant temperature control method based on variable water temperature provided in Embodiment 1 of the present invention;

[0027] Figure 3 This is a flowchart of a water heater constant temperature control method based on variable water temperature provided in Embodiment 2 of the present invention;

[0028] Figure 4 This is a schematic diagram of the control principle of a water heater constant temperature control method based on variable water temperature provided in Embodiment 2 of the present invention;

[0029] Figure 5 This is a flowchart of a water heater constant temperature control method based on variable water temperature provided in Embodiment 3 of the present invention;

[0030] Figure 6 This is a flowchart of a water heater constant temperature control method based on variable water temperature provided in Embodiment 4 of the present invention;

[0031] Figure 7 This is a schematic diagram of a water heater constant temperature control device based on variable water temperature provided in Embodiment 5 of the present invention;

[0032] Figure 8 This is a schematic diagram of the structure of a water heater provided in Embodiment Six of the present invention. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0034] Example 1

[0035] Figure 1 This is a flowchart of a water heater constant temperature control method based on variable water temperature provided in Embodiment 1 of the present invention. This embodiment can be applied to application scenarios of constant temperature control of the outlet water temperature of instant water heaters. The method can be executed by a PID control system configured with specific functional modules.

[0036] like Figure 1 As shown, this method for constant temperature control of a water heater based on variable water temperature specifically includes the following steps:

[0037] Step S1: Obtain the operating parameters of the water heater, including the set temperature, inlet water temperature, outlet water temperature, water flow parameters, and voltage parameters.

[0038] Optionally, a temperature sensor can be used to collect the inlet and outlet water temperatures of the water heater in real time, a water flow sensor can be used to collect the water flow rate of the water heater in real time, a voltage sampling unit can be used to collect the power supply voltage (i.e., mains voltage) of the water heater in real time, and the user-set temperature can be obtained through the system.

[0039] Step S2: Determine the real-time theoretical power value and power control fuzzy value at the sampling time based on the operating parameters.

[0040] In this embodiment, the real-time theoretical power value P0 is the heating power corresponding to the amount of heat absorbed by water to heat it to the set temperature value. It is obtained through pure calculation, which is fast and simple to calculate, and can be used as the basic power value for constant temperature control.

[0041] In this embodiment, the power control fuzzy value is used to reflect the power demand at the current sampling time. For example, a power correction factor can be used as the power control fuzzy value to correct the heating power.

[0042] Specifically, if the power demand value at the current sampling time increases, the power control fuzzy value is increased; if the power demand value at the current sampling time decreases, the power control fuzzy value is decreased.

[0043] Optionally, the fuzzy value for power control can be determined by looking up a table based on the water flow parameters, set temperature, and outlet water temperature.

[0044] Step S3: Establish a mathematical model for water temperature control based on the principle of energy conservation.

[0045] In this embodiment, the water temperature control system of the instantaneous water heater is a multi-input, single-output system, wherein the system inputs include the cold water temperature T. c (t), water flow rate F w (t) and the output power of the thyristor; the system output includes: hot water temperature T h (t). Based on the principle of energy conservation, a mathematical model for water temperature control can be established as shown in Formula 1:

[0046]

[0047] Among them, Q g Let E be the system input heat, η be the system thermal efficiency, t be time, and E be the system thermal efficiency. M (t) represents the rate of change of system energy, c represents the specific heat capacity of water, and t d This is the time constant of the system's lag element.

[0048] Furthermore, to facilitate the research of control algorithms, the mathematical model shown in Formula 1 can be subjected to Laplace transform and simplification to obtain a first-order inertial system with pure time delay. The simplified mathematical model for water temperature control is shown in Formula 2:

[0049]

[0050] in, This is the system proportionality coefficient. Let M be the system time constant and M be the mass of water.

[0051] According to Formula 2, in this water temperature control mathematical model, the system time constant T, the system proportional coefficient K, and the system lag element time constant t are... d All are related to water flow rate F w (t) is related, and based on this, the following step S4 is performed.

[0052] Step S4: Determine the first incremental PID control model based on the operating parameters and the water temperature control mathematical model.

[0053] The incremental PID control algorithm is shown in Formula 3:

[0054] Δu(k)=u(k)-u(k-1)

[0055] =K P [e(k)-e(k-1)]+K I *e(k)+KD *[e(k)-2e(k-1)+e(k-2)] (Formula 3)

[0056] Where u(k) is the control quantity, e(k) is the deviation between the two control quantities, and K P This is the proportional gain coefficient. The integral coefficient is... is the differential coefficient, and T is the sampling period.

[0057] As can be seen from Formula 3, the proportional coefficient, derivative coefficient, and integral coefficient are the key parameters affecting the first incremental PID control model. The parameters of the first incremental PID control model at the sampling time can be determined based on the operating parameters at the sampling time and the water temperature control mathematical model.

[0058] Step S5: Based on the first incremental PID control model, process the temperature difference between the set temperature and the outlet water temperature caused by the water temperature change to obtain the first compensated power control output value.

[0059] Optionally, the water temperature change can be a sudden change in either the set temperature or the inlet water temperature.

[0060] Figure 2 This is a schematic diagram illustrating the control principle of a water heater constant temperature control method based on variable water temperature, provided in Embodiment 1 of the present invention.

[0061] like Figure 2 As shown, in this incremental PID control system, the input parameter r(t) is the set temperature, the control quantity u(t) is the power output value, and the output parameter y(t) is the outlet water temperature. The incremental PID control model adjusts the control quantity u(t) (i.e., the first compensation power control output value) according to the deviation between the set temperature and the outlet water temperature.

[0062] Step S6: Correct the first compensated power control output value according to the power control fuzzy value to obtain the first compensated power correction output value.

[0063] Step S7: Determine the target power value based on the first compensated power correction output value and the real-time theoretical power value.

[0064] Step S8: Drive the heating module to perform heating according to the target power value.

[0065] Optionally, the heating module may include a silicon controlled rectifier (SCR) and a heating element driven by the SCR, wherein the output power of the SCR is equal to the target power value, and the heating element is used to heat cold water in the water heater under the drive of the SCR.

[0066] Specifically, during the operation of the water heater, if the inlet water temperature or the set temperature changes abruptly, the deviation between the input and output of the first incremental PID control model increases. The first incremental PID control model quickly responds to the temperature deviation, adjusts the first compensated power control output value, and determines the current actual required power control fuzzy value by combining the water flow rate at the sampling time and the temperature difference between the set temperature and the outlet water temperature. The product between the first compensated power control output value and the power control fuzzy value is calculated to obtain the first compensated power correction output value. The first compensated power correction output value is used to superimpose and compensate the current real-time theoretical power value to obtain the target power value of the thyristor. Based on this target power value, the heating element is driven to perform heating so that the outlet water temperature follows the set temperature. This solves the problems of slow response speed and poor constant temperature effect of existing constant temperature control algorithms to water temperature changes. By combining fuzzy control with incremental PID control strategy, it can quickly respond to system disturbances, eliminate errors, improve the response speed of power regulation, enhance the stability and robustness of the outlet water temperature, and improve the constant temperature effect.

[0067] Optionally, the real-time theoretical power value and power control fuzzy value at the sampling time are determined based on the operating parameters, including the following steps: establishing a preset fuzzy value table based on the water flow rate and temperature difference; obtaining the temperature difference between the set temperature and the outlet water temperature and the inlet water flow rate; and looking up the preset fuzzy value table based on the inlet water flow rate and temperature difference to determine the power control fuzzy value.

[0068] Specifically, water flow rate and temperature difference are key factors affecting constant temperature control. Based on this, water flow rate and temperature difference can be segmented. By calibrating, recording and storing the power control fuzzy values ​​corresponding to different water flow rates and temperature differences, a preset fuzzy value table can be established. When performing constant temperature control, the actual required power control fuzzy value can be determined by looking up the table.

[0069] For example, if a first water flow threshold and a second water flow threshold (the first water flow threshold being higher than the second water flow threshold) are set to segment the water flow parameters, and a first temperature difference threshold and a second temperature difference threshold (the first temperature difference threshold being higher than the second temperature difference threshold) are set to segment the temperature difference values, then the selection principle for the fuzzy power control value can be set as follows:

[0070] If the inflow rate at the sampling time is higher than the first flow threshold and the temperature difference at the sampling time is higher than the first temperature difference threshold, then the power control fuzzy value is the first correction coefficient.

[0071] If the inflow rate at the sampling time is lower than the second flow threshold and the temperature difference at the sampling time is higher than the first temperature difference threshold, then the power control fuzzy value is the second correction coefficient.

[0072] If the inflow rate at the sampling time is higher than the first water flow threshold and the temperature difference at the sampling time is lower than the second temperature difference threshold, then the power control fuzzy value is the third correction coefficient.

[0073] If the inflow rate at the sampling time is lower than the second flow threshold and the temperature difference at the sampling time is lower than the second temperature difference threshold, then the power control fuzzy value is the fourth correction coefficient.

[0074] The first correction factor is higher than the second, which is higher than the third, which is higher than the fourth, and there are no restrictions on their specific values. For example, the first correction factor can be set to be greater than 1, and the fourth correction factor to be less than 1.

[0075] Therefore, this embodiment optimizes the PID control algorithm calculation value by setting fuzzy values, keeping the output value of the PID control model within a reasonable range under different water temperatures and temperature differences. The algorithm is simple, which helps to improve the system response speed and improve the constant temperature control effect.

[0076] Optionally, the real-time theoretical power value and power control fuzzy value at the sampling time are determined based on the operating parameters, including the following steps: determining the real-time power coefficient based on the voltage parameters; and determining the real-time theoretical power value based on the real-time power coefficient, the set temperature, the inlet water temperature, and the water flow parameters.

[0077] Specifically, if we define the water flow rate as F at the current sampling time... w Set the temperature to T set The inlet water temperature is T in The amount of heat Q required to heat water to the set temperature can be calculated using Formula 4 as shown below:

[0078] Q = c * M * ΔT = c * F w *t*(T set -T in (Formula 4)

[0079] Where c is the specific heat capacity of water, M is the mass of water at the sampling time, and t is the water flow heating time.

[0080] Furthermore, by decomposing Formula 3, we obtain Formula 5 as shown below:

[0081] P0 = A * F w *(T set -T in (Formula 5)

[0082] Where P0 is the real-time theoretical power value at the sampling time, and A is the power coefficient. The power coefficient A is negatively correlated with the voltage value of the voltage parameter. When the voltage value of the voltage parameter is equal to AC 220V (i.e., the mains voltage is AC 220V), the power coefficient A is equal to 70. If the voltage parameter changes, the power coefficient A changes accordingly.

[0083] For example, if the voltage value of the voltage parameter is equal to 220V, then the theoretical real-time power value P0 = 70 * F w *(T set -T in If the voltage parameter is defined as U, then the theoretical real-time power value is...

[0084] Example 2

[0085] Figure 3 This is a flowchart of a water heater constant temperature control method based on variable water temperature provided in Embodiment 2 of the present invention.

[0086] Optionally, such as Figure 3 As shown, the water heater constant temperature control method based on variable water temperature also includes the following steps:

[0087] Step S410: Determine the positional PID control model with hysteresis compensation based on the operating parameters and the water temperature control mathematical model.

[0088] Optionally, the positional PID control model with hysteresis compensation includes a positional PID control model and a hysteresis compensation model. The parameters of the positional PID control model include proportional coefficient, derivative coefficient, and integral coefficient. The hysteresis compensation model is used to estimate the temperature difference between the set temperature and the outlet water temperature, and the estimation result is fed back to the positional PID control system.

[0089] Step S510: Based on the positional PID control model with hysteresis compensation, process the temperature difference between the set temperature and the outlet water temperature to obtain the power control output value.

[0090] Step S610: Determine the target power value based on the first compensated power correction output value, the power control output value, and the real-time theoretical power value, and continue to execute step S8.

[0091] Specifically, in the water temperature control system, there is a pure time lag element. A time lag compensation model is used to predict the dynamic response of the outlet water temperature, and the prediction result is used as feedback to provide to the positional PID control model. The temperature difference between the set temperature and the outlet water temperature is predicted in advance. The positional PID control system adjusts the output value according to the predicted temperature difference, and accumulates the integral part of all predicted temperature differences before the sampling time to obtain the power control output value. The real-time theoretical power value is compensated by this power control output value.

[0092] Optionally, determining a positional PID control model with hysteresis compensation based on operating parameters and a water temperature control mathematical model includes the following steps: adjusting the parameters of the water temperature control mathematical model according to the water flow parameters to obtain a real-time water temperature control mathematical model; determining a hysteresis compensation model based on the real-time water temperature control mathematical model; adjusting the positional PID control parameters based on the water flow parameters, and determining the positional PID control model based on the parameter adjustment results; and establishing a positional PID control model with hysteresis compensation based on the hysteresis compensation model and the positional PID control model.

[0093] Optionally, the lag compensation model can employ the Smith predictor control algorithm. The parameters of the Smith predictor control algorithm can be determined by the transfer function in the process control function that does not contain a pure lag component. The parameters of this transfer function are consistent with the parameters in the water temperature control mathematical model. The system proportional coefficient and system time constant can be calculated by combining Formula 2 above with the real-time sampled water flow to determine the parameters of the lag compensation model.

[0094] Optionally, the correspondence between water flow parameters and positional PID control model can be established through calibration, and the proportional coefficient, derivative coefficient, and integral coefficient of the positional PID control model at the sampling time can be determined by the water flow rate at the sampling time.

[0095] Figure 4 This is a schematic diagram of the control principle of a water heater constant temperature control method based on variable water temperature provided in Embodiment 2 of the present invention.

[0096] Optionally, such as Figure 4 As shown, in this PID control system, the input parameter r(t) is the set temperature, the control quantity u(t) is the power control output value, and the output parameter y(t) is the outlet water temperature. Step S510 includes the following steps: obtaining the estimated deviation function y between the set temperature and the outlet water temperature based on the hysteresis compensation model. τ (t); Obtain the actual temperature difference e1(t) between the set temperature and the outlet water temperature; Based on the actual temperature difference e1(t) and the estimated deviation function y τ (t) Determine the estimated temperature difference e2(t); Based on the positional PID control model, determine the power control output value according to the estimated temperature difference e2(t).

[0097] Specifically, the positional PID control model is shown in Equation 6:

[0098]

[0099] Where e(k) is the deviation value of the input and output (input), u(k) is the control quantity (output), T is the system sampling period, and K is the system output. P This is the proportionality coefficient. T is the integral coefficient. I The integral time constant is... T is the differential coefficient. D is the differential time constant.

[0100] If the pure time delay is defined as τ, then the output y of the lag compensation model (for example, the lag compensation model could be a Smith pure time delay compensator) τ (k) can be expressed by the following formula seven:

[0101]

[0102] Among them, e -τs It is a pure time-delay element in the system.

[0103] If we define the system sampling period as T, perform a Z-transform on Equation 7, and transform the equation after the Z-transform into a difference equation, we can obtain Equation 8 as shown below:

[0104]

[0105] Specifically, based on the water flow rate F at the current sampling time w Determine the parameter values ​​for the positional PID control model and the lag compensation model, and combine them with Formula 8 and the set temperature T at the current sampling time. set With outlet water temperature T in The actual temperature difference e1(t) between the two can be used to obtain the estimated temperature difference e2(t) at the current sampling time. The positional PID control model uses the estimated temperature difference e2(t) as the input parameter to calculate the power control output value, thereby compensating for system errors in advance, avoiding overshoot and response delay caused by control lag, which is conducive to improving the response speed of power regulation and enhancing the constant temperature control effect.

[0106] Optionally, before executing step S610, the method further includes: correcting the power control output value based on the fuzzy power control value to obtain a corrected power control output value; replacing the power control output value with the corrected power control output value; determining the target power value based on the first compensated power correction output value, the corrected power control output value, and the real-time theoretical power value; and continuing to execute step S8. Thus, by performing secondary optimization on the calculation process of position-type PID control through fuzzy control, it is beneficial to improve the system stability and robustness and improve the constant temperature control effect.

[0107] Example 3

[0108] Figure 5 This is a flowchart of a water heater constant temperature control method based on variable water temperature provided in Embodiment 3 of the present invention. Based on the above embodiments, this embodiment adopts a multi-algorithm fusion control strategy such as neural network, incremental PID control, and position PID control. It performs disturbance monitoring based on the fluctuation of multiple parameters of the water temperature control system and compensates the real-time theoretical power value according to the monitoring results.

[0109] Optionally, such as Figure 5 As shown, the water heater constant temperature control method based on variable water temperature also includes the following steps:

[0110] Step S401: Determine the second incremental PID control model based on the changes in water flow parameters.

[0111] Step S402: Based on the second incremental PID control model, process the temperature difference between the set temperature and the outlet water temperature to obtain the second compensated power control output value.

[0112] Step S403: Based on the preset neural network model, the first compensated power correction output value, the power control output value and the second compensated power control output value are weighted and summed to obtain the combined power output value.

[0113] Step S404: Determine the target power value based on the combined power output value and the real-time theoretical power value, and continue to execute step S8.

[0114] In this embodiment, a preset neural network model can be established by debugging and training the neural network model to optimize the weight matrix corresponding to the power control output value, the first compensation power control output value, and the second compensation power control output value. The weight matrix of the preset neural network model is different under different water flow parameters, temperatures, and power, and there is no limitation on this.

[0115] In this embodiment, the parameter values ​​of the second incremental PID control model are determined by combining the changes in water flow parameters and the water temperature control mathematical model.

[0116] When the system experiences a change in water temperature (e.g., a change in inlet water temperature, a change in set temperature, or both), the first incremental PID control model is used to quickly respond to the temperature difference between the outlet water temperature and the set temperature, and adjust the power output value to achieve a rapid response and eliminate system disturbances.

[0117] When the water flow rate of the system changes abruptly, the outlet water temperature will also change abruptly under the existing heating power. The second incremental PID control model is used to quickly respond to the temperature difference between the outlet water temperature and the set temperature and adjust the power output value. After the water flow stabilizes, the power output value of the second incremental PID control model is cleared to zero to avoid affecting the subsequent system. This helps to reduce the error caused by water flow disturbance and improve the system stability.

[0118] Optionally, in this embodiment, the three power control output values, the first compensated power control output value, and the second compensated power control output value can be optimized a second time using power control fuzzy values, and a preset neural network model can be used to perform a weighted summation of the fuzzy control optimized power control output value, the first compensated power control output value, and the second compensated power control output value to obtain a combined power output value.

[0119] Example 4

[0120] Figure 6 This is a flowchart of a water heater constant temperature control method based on variable water temperature provided in Embodiment 4 of the present invention. Based on the above embodiments, this embodiment adopts amplitude limiting control measurement to avoid excessively large algorithm calculation values, control the heating power within a reasonable and stable range, and improve system stability.

[0121] Optionally, such as Figure 6 As shown, the water heater constant temperature control method based on variable water temperature also includes the following steps:

[0122] Step S501: Obtain the preset single-step limit value.

[0123] Step S502: Determine whether the target power value exceeds the preset single-step limit value.

[0124] If the target power value exceeds the preset single-step limit value, then proceed to step S503; otherwise, return to step S502.

[0125] Step S503: Replace the target power value with a preset single-step limit value and drive the heating module to perform heating.

[0126] Specifically, a preset single-step limit value can be set according to the output power limit value of the constant temperature control system. Limit control is performed in each calculation cycle. If the algorithm calculation value exceeds the preset single-step limit value, the preset single-step limit value is used to drive the thyristor to work and realize heating regulation. This helps to avoid the problem of excessive algorithm calculation value caused by integral accumulation and improves system stability.

[0127] Optionally, the constant temperature control method for the water heater further includes: obtaining a preset integral saturation value and determining whether the integral part of the PID control model exceeds the preset integral saturation value; if the integral part exceeds the preset integral saturation value, then in the subsequent closed-loop control loop, the integral coefficient is set to 0, the integral part is discarded, and the cumulative integral value is prevented from reaching saturation, which helps to avoid the problem of excessively large algorithm calculation values ​​and improve system stability.

[0128] Example 5

[0129] Figure 7 This is a schematic diagram of a water heater constant temperature control device based on variable water temperature provided in Embodiment 5 of the present invention. The water heater constant temperature control device based on variable water temperature provided in this embodiment of the present invention can execute the water heater constant temperature control method provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of executing the method.

[0130] like Figure 7 As shown, the water heater constant temperature control device 00 based on variable water temperature includes: a detection unit 10, a theoretical calculation unit 20, a model acquisition unit 30, a power correction unit 40, and a heating drive unit 50. The detection unit 10 is used to acquire the operating parameters of the water heater, including the set temperature, inlet water temperature, outlet water temperature, water flow parameters, and voltage parameters. The theoretical calculation unit 20 is used to determine the real-time theoretical power value and power control fuzzy value at the sampling time based on the operating parameters. The model acquisition unit 30 is used to establish a water temperature control mathematical model based on the principle of energy conservation, and to determine a first incremental PID control model based on the operating parameters and the water temperature control mathematical model. Based on the first incremental PID control model, it processes the temperature difference caused by water temperature changes to obtain a first compensated power control output value, and corrects the first compensated power control output value according to the power control fuzzy value to obtain a first compensated power correction output value. The power correction unit 40 is used to determine the target power value based on the first compensated power correction output value and the real-time theoretical power value. The heating drive unit 50 is used to drive the heating module to perform heating according to the target power value.

[0131] Optionally, the theoretical calculation unit 20 is used to establish a preset fuzzy value table based on the water flow rate and temperature difference; obtain the temperature difference between the set temperature and the outlet water temperature and the inlet water flow rate; and look up the preset fuzzy value table based on the inlet water flow rate and temperature difference to determine the power control fuzzy value.

[0132] Optionally, the theoretical calculation unit 20 is also used to determine the real-time power coefficient based on the voltage parameters; and to determine the real-time theoretical power value based on the real-time power coefficient, the set temperature, the inlet water temperature, and the water flow parameters.

[0133] Optionally, the water heater constant temperature control device 00 further includes: a slow PID model acquisition unit, used to determine a positional PID control model with hysteresis compensation based on operating parameters and a water temperature control mathematical model, and to process the temperature difference between the set temperature and the outlet water temperature based on the positional PID control model with hysteresis compensation to obtain a power control output value; the power correction unit 40 is also used to determine a target power value based on the first compensated power correction output value, the power control output value, and the real-time theoretical power value.

[0134] Optionally, the aforementioned slow PID model acquisition unit is used to adjust the parameters of the water temperature control mathematical model according to the water flow parameters to obtain the real-time water temperature control mathematical model; determine the hysteresis compensation model based on the real-time water temperature control mathematical model; adjust the positional PID control parameters based on the water flow parameters, and determine the positional PID control model based on the parameter adjustment results; and establish a positional PID control model with hysteresis compensation based on the hysteresis compensation model and the positional PID control model.

[0135] Optionally, the aforementioned slow PID model acquisition unit is used to acquire the estimated deviation function between the set temperature and the outlet water temperature based on the hysteresis compensation model; acquire the actual temperature difference between the set temperature and the outlet water temperature; determine the estimated temperature difference based on the actual temperature difference and the estimated deviation function; and determine the power control output value based on the estimated temperature difference using the positional PID control model.

[0136] Optionally, the water heater constant temperature control device 00 further includes: a water flow PID control model acquisition unit and a fusion calculation unit, used to determine a second incremental PID control model based on the change in water flow parameters, and to process the temperature difference between the set temperature and the outlet water temperature based on the second incremental PID control model to obtain a second compensated power control output value; a fusion calculation unit, used to perform a weighted summation of the first compensated power correction output value, the power control output value and the second compensated power control output value based on a preset neural network model to obtain a combined power output value; the power correction unit 40 is also used to determine a target power value based on the combined power output value and the real-time theoretical power value.

[0137] Optionally, the power correction unit 40 is also used to obtain a preset single-step limit value; determine whether the target power value exceeds the preset single-step limit value; if the target power value exceeds the preset single-step limit value, then use the preset single-step limit value to replace the target power value and drive the heating module to perform heating.

[0138] The water heater constant temperature control device based on variable water temperature provided in this invention implements a water heater constant temperature control method based on variable water temperature. It acquires the water heater's operating parameters and determines the real-time theoretical power value and power control fuzzy value at the sampling time based on these parameters. A water temperature control mathematical model is established based on the principle of energy conservation. A first incremental PID control model is determined based on the operating parameters and the water temperature control mathematical model. The temperature difference caused by water temperature changes is processed based on the first incremental PID control model to obtain a first compensated power control output value. The first compensated power control output value is corrected based on the power control fuzzy value to obtain a first compensated power correction output value. A target power value is determined based on the first compensated power correction output value and the real-time theoretical power value. The heating module is then driven to perform heating based on the target power value. This solves the problems of slow response speed and poor temperature control effect of existing constant temperature control algorithms. By combining incremental PID control and fuzzy control, the response speed of power adjustment is improved, the stability and robustness of the outlet water temperature are enhanced, and the temperature control effect is improved.

[0139] Example 6

[0140] Based on the above embodiments, Embodiment Six of the present invention provides a water heater.

[0141] Figure 8 This is a schematic diagram of the structure of a water heater provided in Embodiment Six of the present invention.

[0142] like Figure 8 As shown, the water heater 100 includes the aforementioned water heater thermostat 00 based on variable water temperature.

[0143] The water heater provided in this embodiment of the invention is equipped with a water heater constant temperature control device based on variable water temperature. This device executes a water heater constant temperature control method based on variable water temperature. By acquiring the operating parameters of the water heater, the real-time theoretical power value and power control fuzzy value at the sampling time are determined based on the operating parameters. A water temperature control mathematical model is established based on the principle of energy conservation. A first incremental PID control model is determined based on the operating parameters and the water temperature control mathematical model. The temperature difference caused by water temperature changes is processed based on the first incremental PID control model to obtain a first compensated power control output value. The first compensated power control output value is corrected based on the power control fuzzy value to obtain a first compensated power correction output value. A target power value is determined based on the first compensated power correction output value and the real-time theoretical power value. The heating module is driven to perform heating based on the target power value. This solves the problems of slow response speed and poor constant temperature effect of existing constant temperature control algorithms. By combining incremental PID control and fuzzy control, the response speed of power adjustment is improved, the stability and robustness of the outlet water temperature are enhanced, and the constant temperature effect is improved.

[0144] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A method for constant temperature control of a water heater based on variable water temperature, characterized in that, Includes the following steps: Obtain the operating parameters of the water heater, including the set temperature, inlet water temperature, outlet water temperature, water flow parameters, and voltage parameters; The theoretical real-time power value and power control fuzzy value at the sampling time are determined based on the operating parameters. A mathematical model for water temperature control was established based on the principle of energy conservation. The first incremental PID control model is determined based on the operating parameters and the water temperature control mathematical model. Based on the first incremental PID control model, the temperature difference caused by the water temperature change is processed to obtain the first compensated power control output value; The first compensated power control output value is corrected based on the power control fuzzy value to obtain the first compensated power correction output value; The target power value is determined based on the first compensated power correction output value and the real-time theoretical power value; The heating module is driven to perform heating according to the target power value; The process of determining the real-time theoretical power value and power control fuzzy value at the sampling time based on the operating parameters includes the following steps: A preset fuzzy value table is established based on the magnitude of water flow and temperature difference; Obtain the temperature difference between the set temperature and the outlet water temperature, as well as the inlet water flow rate; The power control fuzzy value is determined by looking up the preset fuzzy value table based on the inlet water flow rate and the temperature difference.

2. The water heater constant temperature control method based on variable water temperature according to claim 1, characterized in that, The process of determining the real-time theoretical power value and power control fuzzy value at the sampling time based on the operating parameters includes the following steps: The real-time power factor is determined based on the voltage parameters; The theoretical value of real-time power is determined based on the real-time power coefficient, the set temperature, the inlet water temperature, and the water flow parameters.

3. The water heater constant temperature control method based on variable water temperature according to claim 1, characterized in that, It also includes the following steps: Based on the operating parameters and the water temperature control mathematical model, a positional PID control model with hysteresis compensation is determined. Based on the positional PID control model with hysteresis compensation, the temperature difference between the set temperature and the outlet water temperature is processed to obtain the power control output value. The target power value is determined based on the first compensated power correction output value, the power control output value, and the real-time theoretical power value.

4. The water heater constant temperature control method based on variable water temperature according to claim 3, characterized in that, The step of determining the positional PID control model with hysteresis compensation based on the operating parameters and the water temperature control mathematical model includes the following steps: The parameters of the water temperature control mathematical model are adjusted according to the water flow parameters to obtain a real-time water temperature control mathematical model; The hysteresis compensation model is determined based on the real-time water temperature control mathematical model. The positional PID control parameters are adjusted based on the water flow parameters, and the positional PID control model is determined based on the parameter adjustment results. Based on the hysteresis compensation model and the positional PID control model, a positional PID control model with hysteresis compensation is established.

5. The water heater constant temperature control method based on variable water temperature according to claim 3, characterized in that, The temperature difference between the set temperature and the outlet water temperature is processed based on the positional PID control model with hysteresis compensation to obtain the power control output value, including the following steps: The estimated deviation function between the set temperature and the outlet water temperature is obtained based on the hysteresis compensation model. Obtain the actual temperature difference between the set temperature and the outlet water temperature; The estimated temperature difference is determined based on the actual temperature difference and the estimated deviation function. The power control output value is determined based on the estimated temperature difference using a positional PID control model.

6. The water heater constant temperature control method based on variable water temperature according to claim 3, characterized in that, It also includes the following steps: The second incremental PID control model is determined based on the changes in the water flow parameters. The temperature difference between the set temperature and the outlet water temperature is processed based on the second incremental PID control model to obtain the second compensated power control output value. Based on a preset neural network model, the first compensated power correction output value, the power control output value, and the second compensated power control output value are weighted and summed to obtain a combined power output value. The target power value is determined based on the combined power output value and the real-time theoretical power value.

7. The water heater constant temperature control method based on variable water temperature according to claim 1, characterized in that, It also includes the following steps: Get the preset single-step limit value; Determine whether the target power value exceeds the preset single-step limit value; If the target power value exceeds the preset single-step limit value, the preset single-step limit value is used to replace the target power value, and the heating module is driven to perform heating.

8. A thermostatic control device for a water heater based on variable water temperature, characterized in that, include: The detection unit is used to acquire the operating parameters of the water heater, including the set temperature, inlet water temperature, outlet water temperature, water flow parameters, and voltage parameters. The theoretical calculation unit is used to determine the real-time theoretical power value and power control fuzzy value at the sampling time based on the operating parameters. Used to establish a preset fuzzy value table based on water flow magnitude and temperature difference magnitude; The temperature difference between the set temperature and the outlet water temperature and the inlet water flow rate are obtained, and the power control fuzzy value is determined by looking up the preset fuzzy value table based on the inlet water flow rate and the temperature difference. The model acquisition unit is used to establish a water temperature control mathematical model based on the principle of energy conservation, determine a first incremental PID control model according to the operating parameters and the water temperature control mathematical model, process the temperature difference caused by water temperature change based on the first incremental PID control model to obtain a first compensated power control output value, and correct the first compensated power control output value according to the power control fuzzy value to obtain a first compensated power correction output value. A power correction unit is used to determine a target power value based on the first compensated power correction output value and the real-time theoretical power value. A heating drive unit is used to drive the heating module to perform heating according to the target power value.

9. A water heater, characterized in that, include: The constant temperature control device for a water heater based on variable water temperature as described in claim 8.

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